Woven wire conveyor belts have been used for many years in the glass and other industries for conveying items through hot and/or caustic environments. Such woven wire conveyor belts are formed of a plurality of interlocked elongated flat spiral annealed steel wire members consisting of a large number of spirals with each spiral comprising spaced essentially linear top and bottom leg portions connected by arcuately curved end portions. The arcuately curved end portions of each elongated flat spiral member are interleaved with the adjacent arcuately curved end portions of the next adjacent elongated flat spiral member and a crimped rod extends through the interleaved portions of the spiral members to retain the elongated flat spiral wire members in position and permit pivotal movement of each elongated flat spiral member with respect to the next adjacent elongated flat spiral member.
It has been conventional practice to form woven conveyor belts of the aforementioned type of annealed steel alloy or other similar relatively pliable wire having a maximum tensile strength in the range of 65,000 to 100,000 pounds per square inch. Each of the flat spiral members is formed by feeding the wire to a flat rotating winding blade supported for rotation on one end and having an opposite end extending through a spiral outfeed guide having a spiral slot surrounding the rotating winding blade. The wire is fed in through the slot of the spiral onto the winding blade. Rotation of the winding blade causes the wire to be wound onto the surface of the winding blade in a configuration following the configuration of the spiral slot of the flat outfeed spiral member so that an elongated flat spiral of wire is formed and moved outwardly to the unsupported end of the rotating winding blade.
Since the wire used in forming the flat spiral members is subject to a substantial amount of bending and tension beyond its elastic limit as it is wound about the rotary winding blade, it is consequently much less difficult to form the flat spiral members of relatively soft wire due to the ease with which such wire can be wound in the necessary spiral formation. It has consequently been the practice in the industry to use relatively soft annealed steel for forming the vast majority of spiral wire members used in conveyor belts. However, annealed wire, which is formed by taking as-drawn wire from the drawing mill, heating same to annealling temperature or higher and then slowly cooling the wire to provide a relatively soft wire, has less tensile strength than the tensile strength of the as-drawn wire from which it is formed notwithstanding the fact that the as-drawn wire and the annealed wire are of identical chemical composition. In addition, the annealling process obviously adds 10% to 15% to the cost of the wire over and above the cost of as-drawn wire and belts formed of the annealed wire are relatively heavy due to the fact that they must be formed of wire of sufficient diameter to provide the required tensile strength for a given conveyor belt installation. Moreover, the heaviness and mass of the presently used conveyor belts formed of annealed steel results in greater power consumption for driving the belts and greater heat absorption than would be the case if the lighter weight materials were employed. Similarly, many installations such as those in the glass industry employ woven conveyor belt conveyors which move through heated areas such as furnaces or lehrs and absorb a substantial amount of heat. Subsequent movement from the heated areas to areas external of the heated areas results in radiation and convection loss of absorbed heat to the surrounding area. Such heat loss is obviously undesirable and is becoming all the more critical in view of the ever increasing cost of fuel. By enabling the use of smaller wire, the present invention lowers the heat loss since there is less thermal storage capacity in the conveyor.
Previous attempts to form elongated flat spiral wire members of as-drawn steel or other similar spring-like wire have not been successful due to the fact that existing wire winding devices and processes for forming the elongated flat spiral members have been incapable of winding spring-like metal into uniform elongated spiral wire members having the uniformity of shape necessary for use in forming woven conveyor belts. The foregoing is true due to the fact that the spiral wire members formed of as-drawn or similar spring-like steel or the like have varied dimensionally in terms of pitch between adjacent spirals and have had internal stresses creating an irregular axial twisting of the spiral members along their lengths so that the spiral members cannot be connected together to form a satisfactory conveyor belt.
Therefore, it is the primary object of this invention to provide a new and improved means and method of forming woven conveyor belts of lighter weight and/or higher strength materials than has been heretofore possible.
Another object of the invention is the provision of a new and improved apparatus and method for forming flattened elongated flat spiral wire members of lightweight high strength material.
Still another object of the invention is the provision of a new and improved apparatus and method for forming elongated flat spiral wire members of spring-like as-drawn steel alloy having a tensile strength in excess of 100,000 to 150,000 pounds per square inch.
Achievement of the objects of this invention is enabled by the preferred embodiment of the subject invention by the provision of unique controlled wire feeding, guiding and bending means for feeding spring-like wire to a conventional forming station consisting of a rotating winding blade extending through a flat spiral outfeed worm member. In the preferred embodiment, unannealed as-drawn steel alloy wire is fed through an elongated linear guide means in which a circular bore is provided with the circular bore being of slightly greater diameter than the diameter of the particular wire being employed so that the wire is fixedly guided along a linear path. The wire leaves the downstream end of the circular bore and passes immediately over bending means consisting of a small diameter roller member about which the wire is bent beyond its elastic limit so as to impart a set bend in the wire. The aforementioned roller means is positioned immediately upstream of the location in a conventional forming station at which the wire extends into the spiral groove of the relatively flat outfeed spiral member and is wound about the winding blade. Winding movement of the wire about the blade results in the wire being bent in the exact opposite direction from the set bend so that the wire is closely configured to the surface of the winding blade.
The basic difference of the invention over the prior art approaches is in the provision of the guide means for completely stabilizing the feed of the wire practically up to the exact point of winding as opposed to the prior systems in which the internal stresses in the wire have been the cause of transverse shift in or whipping movement of the wire as it is fed onto the winding blade. Consequently, variations in internal stress occur at different locations in the finished spiral member to cause resultant undesirable bending and twisting of the spiral. In the present invention, the wire is guided and stabilized along a restricted linear path and then fed immediately over the back bend roller which bends the wire in a vertical plane which restrains the wire from transverse movement so as to prevent whipping of the wire member as has previously occurred with prior known systems. Moreover, the wire as it leaves the back bend roller member immediately engages one side of the groove in the spiral worm so that the wire feed is totally controlled up to the point that the wire is wrapped about the winding blade.